Our laboratory is engaged in a systematic analysis of cellular events in the immune response, the ontogeny of immunocompetent cells and the regulatory mechanisms that control immune responsiveness and unresponsiveness. We will use in vitro culture techniques, cell separation procedures, and a variety of reagents to characterize cell surface markers to T cells and B cells. We will examine T cell heterogeneity, i.e., how far different T cell functions reflect the activities of different subpopulations of thymus-derived cells. BIBLIOGRAPHIC REFERENCES: Dutton, R.W. 1976. The nonspecific T cell signal initiates differentiation. in: The Role of Mitogens in Immunobiology (Oppenheim and Rosenstreich, eds.), Academic Press, New York. Tse, H., and Dutton, R.W. 1976. Separation of helper and suppressor T-lymphocytes on a F1 cell velocity sedimentation gradient. J. Exp. Med. 143 1199.